Electrolysis: processes – compositions used therein – and methods – Electrolytic analysis or testing – For properties of solid material
Reexamination Certificate
1999-01-12
2001-05-01
Warden, Sr., Robert J. (Department: 1744)
Electrolysis: processes, compositions used therein, and methods
Electrolytic analysis or testing
For properties of solid material
C205S775000, C204S401000, C324S514000, C073S038000, C429S006000
Reexamination Certificate
active
06224746
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method and a device for testing the quality of a sheet-like element comprising a membrane.
DESCRIPTION OF THE RELATED ART
A sheet-like element of this type may be, for example, a membrane in itself or else a unit which has further elements in addition to a membrane. One example of such a unit is a membrane/electrode unit (MEU), such as is used in fuel cells. Such an MEU consists of an ion-conductive membrane which is provided with a catalytically active anode on one side and with a catalytically active cathode on the opposite side. In the case of low-temperature fuel cells, polymer electrolyte membranes are used, in which protons are split off from a fuel gas at the anode, the said protons passing through the membrane to the cathode and reacting there with the oxidation gas, whilst at the same time absorbing electrons. In the case of high-temperature fuel cells, ceramic oxide membranes are used, which consist of yttrium-stabilized zirconium oxide and are O
2−
-conductors. DE-PS 4 241 150 discloses methods by which membrane/electrode units can be produced.
It is economically advantageous to produce sheet-like elements comprising a membrane, in the form of large-area initial material, from which individual elements can then be produced in the sizes necessary for the particular actual use.
Separate methods for testing the quality of, in particular, large-area elements are not known at the present time. Operability is checked, as a rule, when the sheet-like element is installed in the suitable size at its intended location, for example in the fuel cell. The disadvantage of this is that faulty sheet-like elements have to be replaced in a time-consuming manner. Moreover, systematic faults in production are detected only at a late stage.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a method and a device of the type mentioned in the introduction, which do not have the disadvantages mentioned above.
In a method of the type mentioned in the introduction, the object is achieved in that the quality test is limited to a part area of the sheet-like element, in that a useful material, provided for the use of the sheet-like element, is fed to one side of the sheet-like element via a useful-material outlet orifice of a housing, the area bounded by the useful-material outlet orifice corresponding to the part area to be tested.
It thereby becomes possible to carry out the quality test on large-area elements. The test may take place randomly, in that the housing is placed onto individual part areas of the sheet-like element. The test may, however, also be carried out with full area coverage, in that a grid of part areas which covers the entire area is predetermined. The method is extremely simple and can therefore also be carried out cost-effectively by placing the housing onto the sheet-like element and feeding it with the useful material. Depending on the function of the sheet-like element, its effectiveness can then be established by means of suitable measures. For the quality check, the transition between the housing and the sheet-like element does not, as a rule, have to be sealed off in a special way. Of course, if hazardous and/or liquid useful materials are used, a sealing-off may be carried out, for example by the useful-material outlet orifice being bounded by means of a flexible material.
The method according to the invention may advantageously also be designed in such a way that the quality test is carried out during the production of the sheet-like element.
It follows directly from this that the method according to the invention may also be designed in such a way that the results of the quality test are used for the control of production parameters. In this way, faults in the production of the sheet-like element can be detected quickly and the production parameters adapted in order to improve the product.
Furthermore, it may be advantageous to design the method according to the invention in such a way that the sheet-like element is moved relative to the housing during the quality test. This is advantageous particularly when the sheet-like element is produced in the form of band material. The sheet-like element can then run past the housing, so that a continuous strip of the band material is checked by means of the housing and the housing does not have to be moved for this purpose.
If the sheet-like element comprises a membrane permeable to material, the method according to the invention may also be designed in such a way that the permeability of the membrane to the useful material is tested, the quantity of useful material which passes through the membrane in the region of the part area per unit time being detected on the other side of the sheet-like element.
It may be advantageous, in particular, to design the method according to the invention in such a way that the sheet-like element is a membrane/electrode unit (MEU) suitable for use in fuel cells and having electrode elements on both sides of the membrane, the useful material is a fuel gas fed to the housing at a specific partial pressure, the other side of the MEU is supplied with oxidation gas of a specific partial pressure and an electrical voltage generated between the electrode elements of the two sides of the MEU and/or an electrical current flowing between the electrode elements is measured.
In the case of a fuel cell which is operated with hydrogen and oxygen, atmospheric oxygen may be used as the oxidation gas. That is to say, it is sufficient merely to feed the fuel gas via a housing in a controlled manner, whilst the supply of oxidation gas on the other side of the MEU is ensured by the ambient atmosphere.
The method according to the invention may, however, also be designed in such a way that oxidation gas is fed to the other side of the MEU, opposite the useful-material outlet orifice, via an oxidation-gas outlet orifice of an oxidation-gas housing, the oxidation-gas outlet orifice corresponding in its dimensions to the useful-material outlet orifice. The partial pressure of the oxidation gas can thereby be checked effectively and, if appropriate, varied in a controlled manner.
The abovementioned object is achieved by means of a device comprising a housing with a plane useful-material outlet orifice and with a useful-material inlet orifice, a useful-material source and a useful-material conduit connecting the useful-material source to the useful-material inlet orifice.
It may be advantageous to design the device according to the invention in such a way that, in the case of a gaseous useful material, means for regulating and means for determining the useful-material partial pressure prevailing in the housing are provided.
In the case of a sheet-like element with a membrane permeable to material, the device according to the invention may be designed in such a way that, in order to test the permeability of the membrane to the useful material, means for detecting the quantity of useful material which passes through the membrane per unit time are provided.
Furthermore, it may be advantageous to design the device according to the invention in such a way that, in order to test a membrane/electrode unit (MEU) suitable for use in fuel cells and having electrode elements on both sides of the membrane, at least one anode contact element and at least one cathode contact element for electrical contacting with the electrode elements and means for determining a voltage prevailing between the electrode elements of the two sides and/or a current flowing between the electrode elements are provided.
If the electrode elements on the two sides of the MEU are sheet-like, simple wire-shaped elements, which rest resiliently on the MEU, are sufficient for the voltage pick-up.
The device according to the invention may advantageously be designed in such a way that the anode contact element located in the housing is designed as a drum-shaped hollow body and is mounted rotatably, the hollow body is permeable to fuel gas at least on its circumference provid
Kabs Hermann
Meissner Dieter
Forschungszentrum Julich GmbH
Nath Gary M.
Nath & Associates PLLC
Novick Harold L.
Olsen Kaj K.
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